Numerous treatments, both topical and systemic, are available for the primary and secondary skin infection caused by sensitive Gram +ve organisms such as Staphylococcus aureus, Streptococcus spp etc. Topical and systemic bacterial infection treatment compositions typically employ at least one active pharmaceutical ingredient (API) in combination with a base component. In the cream form, the APIs typically comprise an antibiotic/antibacterial such as Fusidic acid and the like.
In the currently available Fusidic acid creams, Fusidic acid in fine powder form is used as source API. The small particle size enhances its dermal contact by providing a large specific surface area and penetration, and provides a smooth feel on application to skin. However, a serious shortcoming of the fine size of Fusidic acid particles is that it presents an enormous surface area for contact and reaction with molecular Oxygen during manufacture, handling, and processing of the cream. This has serious implications to its chemical stability and results in rapid reduction in potency of the API (Fusidic acid) in the final cream formulation. Degradation due to oxidation is a major cause of instability of currently available Fusidic acid creams. Table 1 show that the degradation in the API samples (Fusidic acid) exposed to oxygen ranged between 7.7% and 11% for conditions ranging from room temperature to 45° C. when analysed at three months of exposure period at the above conditions.
It is known that greater the exposure time of Fusidic acid as the raw API to Oxygen, greater the limitations on stabilising Fusidic acid in a formulation. However, there is no published data on the stability of Fusidic acid over a period of time.
As an alternative to Fusidic acid, Sodium Fusidate is known to have been used to make dermaceutical medicaments for topical application. However, these are in the form of ointment rather than cream. Drawbacks of ointments over creams are well known and it's generally preferable to use creams rather than ointments for topical application.
Several aspects of Fusidic acid as an API are known:                It is thermolabile        It is available in cream formulations        It can be obtained from Sodium Fusidate by dissolving the latter in an aqueous phase and adding acid to the solution, whereby Fusidic acid precipitates. However, the Fusidic acid precipitate is difficult to process into a cream form first due to its coarse and uneven particle size and second retrieving Fusidic acid from wet cake involves drying and further handling which deteriorates the Fusidic acid due to exposure to oxygen        The stability of the API in a Fusidic acid cream is unreliable due to the thermolabile nature of Fusidic acid        
Stabilization of medicaments containing Fusidic acid against oxidation involves observing a number of stringent precautionary procedures during manufacture and storage. These include:                replacing Oxygen in pharmaceutical containers with inert gases such as Nitrogen, Carbon dioxide, Helium and the like        avoiding contact of the medicament with heavy metal ions which catalyze oxidation,        storing the API at reduced temperatures throughout its shelf life before processing        
In practice this means stricter controls during the manufacture as well as storage of such API (storing it typically at 2° C. to 8° C. in air-tight containers throughout their shelf life).
There is therefore a need to provide a process of making a Fusidic acid cream in which Fusidic acid will be of greater stability than the stability of the Fusidic acid in the conventional creams, particularly at the time of the manufacture of the cream, and which will sustain its stability at an acceptable level throughout its shelf life.